Los Angeles police say a city utility truck hit and killed a 17-year-old boy who was heading to school because he apparently didn't know a threat had shut down all campuses.

Detective Charles Walton says the crash happened at an intersection around 7:10 a.m. Tuesday. A short time earlier, the superintendent of the Los Angeles Unified School District announced that schools would not open due to an emailed threat.

Walton says all indications show that the student was heading to school rather than away from it and that he had not yet found out that classes were canceled for the day.

Administrators of nearby Los Angeles International Charter High School tell the Los Angeles Times that the teen was a student there.

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2:15 p.m.

After getting word that all Los Angeles schools were shutting down because of a threat of possible attack, many parents' first thoughts were about how to discuss the situation with their kids.

Lupita Vela says her 8-year-old daughter enjoys attending Eagle Rock Elementary, and Vela was worried about the third-grader feeling unsafe in class after learning of the threat Tuesday.

Experts say parents should first reassure themselves by getting as much information as possible about potential risks. Then sit down with the child and find out his or her specific fears.

The ranking Democrat on the House Select Committee on Intelligence says the threat that shut down the Los Angeles school system is believed to be a hoax.

U.S. Rep. Adam Schiff, D-Calif., said a preliminary investigation indicates that the threats in Los Angeles and New York City were designed to disrupt school districts in large cities.

He says in a statement Tuesday that investigators are still gathering information about the origin of the threats.

Officials have said the threats targeted students and involved gun attacks and explosive devices. It led Los Angeles school officials to close more than 900 public schools and 187 charter schools.

New York City officials say they received the same threat as Los Angeles but quickly concluded it was a hoax.

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11:30 a.m.

A threatening email sent to the New York City school superintendent warned that every school in the city would be attacked with pressure cooker bombs, nerve gas agents, machine pistols and machine guns.

The email was sent early Tuesday and said the writer and "138 comrades" would carry out the attack. It said, "The students at every school in the New York City school district will be massacred, mercilessly. And there is nothing you can do to stop it."

The anonymous writer claimed to be a student at a district high school who had been bullied.

A law enforcement official with access to the document provided the email to The Associated Press. The official wasn't authorized to disclose details of an ongoing investigation and spoke on condition of anonymity.

— From Associated Press writer Colleen Long in New York

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11:20 a.m.

The Los Angeles police chief says the emailed threat that shut down the nation's second-largest school district described an attack with assault rifles.

Chief Charlie Beck said Tuesday that it was specific to all the campuses in the Los Angeles Unified School District. He says the email's "implied threat" involved explosive devices and the "specific threat" was a shooting attack.

Beck says the email was routed through Germany but that police believe its origin was much closer.

The police chief says the city takes threats against its schools seriously given the recent attack in San Bernardino and the frequency of school shootings.

He says the LAPD gave advice to district officials, who then chose to close all of its more than 900 schools and 187 public charter schools. Beck defended that decision.

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10:45 a.m.

The White House says the different reactions taken by the nation's two largest public school systems after receiving threats show that local first-responders are responsible for protecting their communities.

Spokesman Josh Earnest says he won't "second-guess" the decisions by Los Angeles officials to close their schools and New York City officials to keep their students in class.

Earnest says local authorities make decisions based on information they receive and what they believe is in the best interests of their communities.

He says that the FBI has been in touch with California law enforcement authorities.

New York City officials say they received the same threat as Los Angeles but quickly concluded it was a hoax. New York Police Commissioner William Bratton said he thought Los Angeles overreacted.

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10:35 a.m.

Los Angeles law enforcement and city leaders are defending the decision to shut down the city's school system due to an emailed threat.

Police Chief Charlie Beck and Mayor Eric Garcetti told reporters Tuesday that they stand behind the superintendent's order to close the Los Angeles Unified School District's more than 900 schools and 187 public charter schools as a precaution.

New York City officials say they and many cities nationwide received the same threat and quickly determined it was a hoax.

Beck says it's easy to criticize a decision when someone has no responsibility for its outcome. He says district police contacted his department late Monday about a threat sent to school board members.

Officials say it was a tough decision but the safety of students and employees was their main concern.

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9:40 a.m.

New York City officials say they and many cities across the country received the same threat that closed the Los Angeles school system.

Mayor Bill de Blasio told reporters Tuesday that the threat came in the form of a "generic" email and that New York officials quickly concluded that it wasn't credible.

Los Angeles Unified School District officials say they closed all of the system's more than 900 schools and 187 public charter schools as a precaution.

A law enforcement official briefed on the investigation said the threat involved bombs in students' backpacks. The official wasn't authorized to speak about an ongoing investigation and insisted on anonymity.

District spokeswoman Shannon Haber says the threat was emailed to a school board member late Monday.

— From Associated Press writer Tami Abdollah in Washington, D.C.

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9:20 a.m.

A Los Angeles school official says the threat that shut down the nation's second-largest school district was emailed to a school board member and is believed to have come from an IP address in Frankfurt, Germany.

Los Angeles Unified School District spokeswoman Shannon Haber said Tuesday that she didn't know if the district has ever closed all of its more than 900 schools and 187 public charter schools.

New York City officials say they received the same threat but quickly concluded that it was a hoax. New York Police Commissioner William Bratton said he thought Los Angeles officials overreacted by deciding to close the schools.

Haber says she couldn't comment on threats received by other districts and whether they're related.

She says, "At this point, we're focused on LA Unified."

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8:55 a.m.

New York City officials say they received the same threat that led to the closure of the Los Angeles school system but quickly concluded that it was a hoax.

Mayor Bill de Blasio said Tuesday morning that he was "absolutely convinced" there was no danger to schoolchildren in New York.

New York Police Commissioner William Bratton said he thought Los Angeles officials overreacted by deciding to close the nation's second-largest school system.

He said a school superintendent received the threatening email Tuesday morning.

Bratton said the person who wrote the note claimed to be a jihadist but made errors that made it clear the person was a prankster.

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8:15 a.m.

Parents bundling up their children on an unusually cold morning received robocalls from Los Angeles schools officials telling them to keep them home.

A voice message from the LA Unified School District said: "As a result of a threat received the superintendent has directed all schools to be closed today." Some parents also got separate calls from the schools themselves.

Parent Lupita Vela says she was terrified after getting the announcement, especially in light of the recent San Bernardino attack. Vela says she worries about how to talk to her 8-year-old daughter, Isabella, about the threat because she wants the third-grader to feel safe at school.